1. Field of the Invention
This invention relates generally to a reed operating system for a loom, and more particularly to a mechanism for altering the advance position of a reed without largely altering the backdown position of the reed.
2. Description of the Prior Art
A variety of reed operating systems for weaving looms have been proposed and put into practical use. Typical one of them is schematically shown in FIG. 8. The reed operating system in FIG. 8 includes a driving cam 101 rotatably mounted to a frame of a loom. A swingable lever 102 is swingably driven through a cam follower 102a by the driving cam 101. The swingable lever 102 is pivotted at its pivot section 102b. A sley sword 103 is pivotted at the common pivot section 102b and provided with a reed 104. The sley sword 104 functions to beat up a picked weft yarn against a cloth fell 106 of a woven fabric 107 which is contiguous with shedded warp yarns 105. Additionally, links 108 and 109 are connected with each other by a connecting pin 110. The link 108 is connected at its free end section with the free end section 102c of the lever 102, while the link 109 is connected at its free end section with a middle projection 103a of the sley sword 103. With such a reed operating system, the advance (bearing-up) position of the reed 104 is suitably set by selecting the location of the connecting pin 110.
However, the above-discussed conventional reed operating system is such configurated as to fundamentally alter the length of a connecting rod constituted of the links 108, 109 or an angle between the lever 102 and the sley sword 103 by selecting the location of the connection pin 110. Therefore, if the advance position of the reed 104 is altered from A.sub.1 to B.sub.1 in FIG. 8, the backdown position of the reed is also unavoidably altered from A.sub.2 to B.sub.2. Such alteration of the advance and backdown positions of the reed determines that a time period in which weft picking is possible is within an angle .theta. corresponding to a region between B.sub.2 and A.sub.1, thereby reducing the weft picking possible time period.
In order to prevent the weft picking possible time period or angle .theta. from reducing, it is necessary that the altered backdown position B.sub.2 is near the previous backdown position A.sub.2 even in case the advance position of the reed is altered from A.sub.1 to B.sub.1. Additionally, for the above arrangement in which the backdown position of the reed is altered, it is necessary to set the operation of a shedding motion in conformity with the backdown position of the reed at the time the length of the connecting rod becomes the smallest. This unavoidably enlarges the size of a warp shed.